Generation of lipid peroxyl radicals from edible oils and their biological activities: a need for consideration for anti-radical components and purification processing

Amino acid and peptide hemin derivatives as new promising virucidal agents

We synthesized a series of hemin derivatives (HDs) substituted by residues of amino acids and peptides at either one or two propionic-acid residues, and studied the virucidal activity of the compounds obtained against herpes simplex virus. Compounds 6,7-bis-(methyl ester N0L-seryl)-protohemin (IX) (2) and 6,7-bis-[methyl ester N0-L-arginyl)-protohemin (IX) (6) shown the highest virucidal activity. We also investigated the interaction between HDs and lipid-membrane components as a possible mechanism of virucidal action. A model system including Clark's electrode and a micellar solution of methyl linoleate was used to quantitatively assess the capability of HDs to catalyze the oxidation of polyunsaturated fatty acids as components of lipid membranes. Another model system including liposomes that consisted of dioleoylphosphatydylcholine and was loaded with the fluorescent dye carboxyfluorescein was employed to examine the effect of HDs on lipid-membrane permeability. The kinetics and efficacy of increasing liposome-membrane permeability on exposure to HDs appeared to depend on the nature of the substituents in the HDs. The findings are strongly suggestive of the presence of two different modes of interaction between an HD and the lipid membrane, i.e. oxidative and non-oxidative mechanisms possibly underlie the virucidal action of HDs.

Fluorescence light-up recognition of DNA nucleotide based on selective abasic site binding of an excited-state intramolecular proton transfer probe

DNA single-nucleotide polymorphism (SNP) detection has attracted much attention due to mutation-related diseases. Various fluorescence methods for SNP detection have been proposed and many are already in use. However, fluorescence enhancement for signal-on SNP identification without label modification still remains a challenge. Here, we find that the abasic site (AP site) in a DNA duplex can be developed as a binding pocket favorable for the occurrence of the excited-state intramolecular proton transfer (ESIPT) of a 3-hydroxyflavone, fisetin, which is used as a proof of concept for effective SNP identification. Fisetin binding at the AP site is highly selective for target thymine or cytosine facing the AP site by observation of a drastic increase in the ESIPT emission band. In addition, the target recognition selectivity based on this ESIPT process is not affected by flanking bases of the AP site. The binding selectivity of fisetin at the AP site is also confirmed by measurements of fluorescence resonance energy transfer, emission lifetime and DNA melting. The fluorescent signal-on sensing for SNP based on this fluorophore is substantially advantageous over the previously used fluorophores such as the AP site-specific signal-off organic ligands with a similar fluorescing mechanism before and after binding to DNA with hydrogen bonding interaction. We expect that this approach will be employed to develop a practical SNP detection method by locating an AP site toward a target and employing an ESIPT probe as readout.

Antioxidant activity of vinegar produced from distilled residues of the Japanese liquor shochu

Rice shochu distilled residue (RSDR) is a byproduct of rice shochu production. RSDR was converted into vinegar by acetate fermentation. In our present study, two major antioxidant compounds, tyrosol and ferulic acid, were identified from the RSDR-derived vinegar. Furthermore, we investigated the antioxidant activity of freeze-dried RSDR-derived vinegar, which was Acetobactor aceti fermentation powder (AFP), in vitro and in vivo. AFP at 0.25 mg/mL or higher concentrations showed an inhibitory effect against lipid peroxidation and cellular GSH depletion in HepG2 cells induced by H(2)O(2) (P < 0.05). We thus considered the potential of AFP in protecting cells against damage induced by H(2)O(2). Its antioxidant activity was evaluated in vivo using carbon tetrachloride (CCl(4))-induced acute liver injury mouse models. Five consecutive days of oral preadministration of AFP dissolved in PBS at 200, 400, and 800 mg/kg body weight significantly suppressed lipid peroxidation in the liver induced by CCl(4) (P < 0.01). Consequently, treatment with AFP at 200 mg/kg body weight or higher doses suppressed the elevation of alanine aminotransferase and aspartate aminotransferase levels in serum (P < 0.05). These findings suggest that RSDR-derived vinegar can be developed as a health food with an antioxidant effect for the prevention of oxidative injury and cancer.

Antioxidant activity of a novel extract from bamboo grass (AHSS) against ischemia-reperfusion injury in rat small intestine

Production of free radical species in cells and body tissues is known to cause many pathological disorders. Therefore, free radical scavengers play an important role in the prevention of various human diseases. Bamboo grass, Sasa senanensis, is a native Japanese plant. Sasa has been used for medicine in Japan for many centuries. In this study, we investigated the antioxidative activity of Absolutely Hemicellulose Senanensis (AHSS), a novel extract from Sasa. In the first part of this study, we found that AHSS has antioxidant activities by the assay using superoxide anion-2-methyl-6-methoxyphenylethynylimidazopyrazynone (MPEC) reaction kit. We then confirmed its antioxidative activity using a rat ischemia and subsequent reperfusion (I/R) injury model. Breakdown of the intestinal wall caused by intestinal I/R was attenuated by pretreatment with AHSS. Moreover, AHSS inhibited the production of lipid peroxide by intestinal I/R. AHSS could be an important source of ingredients for use in functional foods and other applications.

Oxidative modification of rat eye lens proteins by peroxyl radicals in vitro: protection by the chain-breaking antioxidants stobadine and Trolox

In an attempt to model the processes of free radical-mediated cataractogenesis, we investigated the oxidative modification of rat eye lens proteins by peroxyl radicals generated by thermal decomposition of 2,2'-azobis(2-amidinopropane)hydrochloride (AAPH) under aerobic conditions. When incubated with AAPH, the soluble eye lens proteins precipitated in a time-dependent manner. The insolubilisation was accompanied by the accumulation of protein free carbonyls and the diminution of sulfhydryls, yet the processes were shifted in time. The SDS-PAGE analysis of the AAPH-treated proteins revealed the presence of high molecular weight cross-links and, to a lesser extent, fragments. The aggregation and cross-linking of proteins along with the generation of free carbonyls was significantly inhibited by the chain-breaking antioxidants stobadine and Trolox. On the other hand, the AAPH-initiated sulfhydryl consumption was much less sensitive to the antioxidants studied. The results point to a complex mechanism of peroxyl-radical-mediated modification of eye lens proteins with implications for cataract development and they indicate a potentially protective role of antioxidants.

Postprandial lipid oxidation and cardiovascular disease risk

A mild pro-oxidative state accompanies meal ingestion, which results in an increase in biomarkers of inflammation, adhesion, and endothelial dysfunction, all of which are factors in the development of cardiovascular disease. Both fat and carbohydrate can cause the effect, which is additive and exacerbated by diabetes. The presence of lipid, glucose, and cholesterol oxidation products of dietary or endogenous origin may contribute to postprandial oxidative stress. However, the generation of excess superoxide due to abundant energy substrate after the meal may be a predominate factor resulting in oxidative stress and a decrease in nitric oxide, which is important to endothelial function. Remediation of postprandial oxidative stress through direct reduction of superoxide generation and simultaneous consumption of antioxidants with each meal should be a focus of future research.

Antioxidative and antimutagenic activities of 4-vinyl-2,6-dimethoxyphenol (canolol) isolated from canola oil

A potent antioxidative compound in crude canola oil, canolol, was recently identified, and reported herein are studies of its scavenging capacity against the endogenous mutagen peroxynitrite (ONOO(-)). ONOO(-) is generated by the reaction between superoxide anion radical and nitric oxide, both of which are produced by inflammatory leukocytes. Among various antioxidative substances of natural or synthetic origin, canolol was one of the most potent antimutagenic compounds when Salmonella typhimurium TA102 was used in the modified Ames test. Its potency was higher than that of flavonoids (e.g., rutin) and alpha-tocopherol and was equivalent to that of ebselen. Canolol suppressed ONOO(-)-induced bactericidal action. It also reduced intracellular oxidative stress and apoptosis in human cancer SW480 cells when used at a concentration below 20 microM under H(2)O(2)-induced oxidative stress. In addition, canolol suppressed plasmid DNA (pUC19) strand breakage induced by ONOO(-), as revealed by agarose gel electrophoresis.

Meat and cancer: haemoglobin and haemin in a low-calcium diet promote colorectal carcinogenesis at the aberrant crypt stage in rats

High intake of red meat, but not of white meat, is associated with an increased risk of colon cancer. However, red meat does not promote cancer in rodents. Haemin, added to low-calcium diets, increases colonic proliferation, and haemoglobin, added to high-fat diets, increases the colon tumour incidence in rats, an effect possibly due to peroxyl radicals. We thus speculated that haem might be the promoting agent in meat, and that prevention strategies could use calcium and antioxidants. These hypotheses were tested in rats at the aberrant crypt foci (ACF) stage at 100 days. F344 rats (n = 124) were given an injection of azoxymethane and were then randomized to 11 groups fed with low-calcium (20 micro mol/g) AIN76-based diets, containing 5% safflower oil. Haemin (0.25, 0.5 and 1.5 micro mol/g) or haemoglobin (1.5 and 3 micro mol haem/g) was added to five experimental diets, compared with a control diet without haem. Three other high-haemin diets (1.5 micro mol/g) were supplemented with calcium (250 micro mol/g), antioxidant butylated hydroxyanisole and rutin (0.05% each), and olive oil, which replaced safflower oil. Faecal water was assayed for lipid peroxidation by thiobarbituric acid reactive substances (TBARs) test, and for cytolytic activity. Haemin strikingly increased the ACF size, dose-dependently, from 2.6 to 11.4 crypts/ACF (all P < 0.001). The high-haemin diet also increased the number of ACF per colon (P < 0.001). Promotion was associated with increased faecal water TBARs and cytotoxicity. Calcium, olive oil and antioxidants each inhibited the haemin-induced ACF promotion, and normalized the faecal TBARs and cytotoxicity. The haemoglobin diets increased the number of ACF and faecal TBARs, but not the ACF size or the faecal cytotoxicity. In conclusion, dietary haemin is the most potent known ACF promoter. Haemoglobin is also a potent promoter of colorectal carcinogenesis. The results suggest that myoglobin in red meat could promote colon cancer. Diets high in calcium, or in oxidation-resistant fats, may prevent the possible cancer-promoting effect of red meat.